NEW YORK (JTA) — In laying the legal groundwork for a massive raid of the country’s largest kosher slaughterhouse, federal authorities cited claims that illegal narcotics production took place at the factory and hundreds of illegal immigrants were employed there, including several of the rabbis responsible for kosher supervision.

The charges were among the most explosive details to emerge following the raid Monday at the Agriprocessors plant in Postville, Iowa.

Agents arrested 390 workers in what Immigration and Customs Enforcement called the largest raid of its kind in U.S. history.

The raid, which required federal authorities to rent an expansive fairground in nearby Waterloo to house detainees, prompted the U.S. District Court for the Northern District of Iowa to temporarily relocate judges and court personnel to the site because the facilities in Cedar Rapids and Sioux City were inadequate.

“There have been other operations where more people have been arrested,” Tim Counts, an Immigration and Customs Enforcement spokesman, told JTA. “But as far as we can determine, this is the largest single-site operation as far as number of arrests go.”

The raid follows a six-month investigation involving more than a dozen federal agencies, including the Federal Bureau of Investigation, the Drug Enforcement Administration, the Internal Revenue Service, and the departments of labor and agriculture.

Three Israelis and four Ukrainians were among the detainees held on charges of being in the country illegally, Counts said. Officials are expected to bring criminal charges against some of the detainees as well, most of whom are from Guatemala and Mexico.

Agriprocessors said in a statement Tuesday that it “takes the immigration laws seriously” and intended to “continue to cooperate with the government in its investigation.”

“Agriprocessors will also inquire further into the circumstances that led to these events,” the company said. “We extend our heartfelt sympathies to the families whose lives were disrupted and wish them the best. We are deeply committed to meeting the needs of all of our customers and are operating again today.”

In the affidavit filed as part of the 60-page application for a search warrant, additional details were revealed of the government’s investigation of Agriprocessors, a company that has been beset by numerous allegations of health and safety violations, mistreating workers and using controversial slaughter practices.

According to the document, a former supervisor at the plant — identified only as Source #1 — told investigators that some 80 percent of the workforce was illegal.

The source also said he believed rabbis responsible for kosher supervision entered the United States from Canada without proper immigration documents. According to the affidavit, the source did not provide evidence for his suspicions about the rabbis.

Source #1 also claimed to have discovered active production of the drug methamphetamine at the plant and reported incidents of weapons being carried there.

Methamphetamine, more commonly known as crystal meth, is Illegal in the United States. The popular nightclub drug gives users a sense of energy and euphoria that can last for hours.

Agriprocessors employees told investigators that sometimes they were required to work nighttime shifts of 12 hours or more.

The affidavit says that 697 plant employees are believed to have violated federal laws.

With Agriprocessors producing more than half of the nation’s kosher meat, the raid has prompted fears of a disruption in supply. Though the plant was back in operation Tuesday, it was unclear if Agriprocessors could meet its normal production capacity with hundreds of its workers in federal custody.

Founded by Brooklyn butcher Aaron Rubashkin, Agriprocessors produces kosher meat and poultry marketed under the labels Aaron’s Best and Rubashkin’s.

The firm gained national attention in 2000 with the publication of the book “Postville,” which described the tensions between the company and the local community. The company has attracted a significant population of Orthodox Jews to a rural pocket of northeast Iowa.

Agriprocessors did not respond to requests for comment from JTA. Asked if there was slaughter taking place Tuesday, a woman who answered the phone at the plant said, “We’re trying.”

The Des Moines Register reported that more than 100 cars were in the company lot Tuesday morning, but quoted a nearby business owner who said that foot and vehicular traffic to the plant was much lower than usual.

Rabbi Menachem Genack, the head of the Orthodox Union’s kosher supervision department — the largest outfit certifying the kosher status of Agriprocessors’ meat — told JTA that other companies had assured him that they could make up for any shortfall from the Postville plant.

Genack reiterated the O.U.’s policy of leaving matters of immigration and labor standards to the government.

“No one else has the resources to do what the federal government can do,” he said.

If the company turns out to be criminally liable, Genack said, that could be grounds for losing its kosher certification.

Genack said he was told by the plant’s supervising rabbi that two foreign rabbis working at the plant had failed to renew their work permits when they expired a few weeks ago. He described the issue as a “technical” violation and insisted the two rabbis had not been detained.

Much of the information the government collected appears to have come from former employees of Agriprocessors who were detained by police on unrelated charges. Sources related similar stories of presenting fraudulent documents and Social Security numbers when seeking employment with the company.

Several said they were aware of undocumented workers employed at the plant that were paid by supervisors in cash.

The affidavit says the government has probable cause to believe that an Agriprocessors supervisor assisted workers in acquiring fake documents in exchange for a cut of the proceeds.

Federal investigators provided documentation for a former Agriprocessors employee, identified in the affidavit as Source #7, for the purpose of gaining employment at the plant. Once hired, the source reported on rabbis who insulted the workers and threw meat at them.

In one alleged instance, a “Hasidic Jew” duct-taped a worker’s eyes and then hit him with a meat hook, “apparently not causing serious injuries.”

Agriprocessors has come under fire before for its labor practices, as well as health and safety violations. In March, authorities fined the company $182,000 for violations at the plant.

People for the Ethical Treatment of Animals has clandestinely videotaped a controversial slaughter practice used at the plant.

In addition, an investigation by the Forward weekly newspaper revealed allegations that employees were underpaid and exploited. Agriprocessors officials denied the allegations.

On Tuesday, members of the Conservative movement’s Hekhsher Tzedek Commission condemned the company, saying that keeping kosher requires more than just adherence to ritual matters, but also sensitivity to the environment and respect for workers and animals. The Hekhsher Tzedek initiative is in part a response to past allegations of misconduct at Agriprocessors.

“The actions of this company have brought shame upon the entire Jewish community,” the commission said. “Yesterday’s discovery, along with the other violations of the ethical standards set forth by our Torah and our tradition underscore the need for Hekhsher Tzedek. To be sure, halacha has never limited its concern to the ritual elements of kashrut alone.”

Tell Me More, May 9, 2008 · Hundreds – and, perhaps, thousands – of Jewish converts may soon have their status invalidated. The High Rabbinical Court in Israel has questioned the integrity of an official who oversaw their conversions. Rabbi Shaul Farber, director of the Jewish Life Information Center and Shaney Gilbert, who converted to Judaism 2005, discuss the case and its implications.

*One glaring hypocrisy (Christian Inquisitions regarding the sincerity of conversion are to be condemned, but Judaic Inquisitions regarding the sincerity of conversion are quite kosher) and one glaring omission (a description of the ritual of conversion, a lingering physical inspection of the nude female convert by three rabbis in a bath otherwise alone).